From 8dd87f3c5283de7f95396a236e420487226f3951 Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Sun, 17 Jul 2022 17:45:05 -0500 Subject: [PATCH] dm: Allow dm_call_pr to be used for path searches The specs state that if you send a reserve down a path that is already the holder success must be returned and if it goes down a path that is not the holder reservation conflict must be returned. Windows failover clustering will send a second reservation and expects that a device returns success. The problem for multipathing is that for an All Registrants reservation, we can send the reserve down any path but for all other reservation types there is one path that is the holder. To handle this we could add PR state to dm but that can get nasty. Look at target_core_pr.c for an example of the type of things we'd have to track. It will also get more complicated because other initiators can change the state so we will have to add in async event/sense handling. This commit, and the 3 commits that follow, tries to keep dm simple and keep just doing passthrough. This commit modifies dm_call_pr to be able to find the first usable path that can execute our pr_op then return. When dm_pr_reserve is converted to dm_call_pr in the next commit for the normal case we will use the same path for every reserve. Signed-off-by: Mike Christie Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 50 ++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 38 insertions(+), 12 deletions(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index e44415d..15fc2ea 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -3077,10 +3077,11 @@ struct dm_pr { u64 new_key; u32 flags; bool fail_early; + int ret; }; static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn, - void *data) + struct dm_pr *pr) { struct mapped_device *md = bdev->bd_disk->private_data; struct dm_table *table; @@ -3105,7 +3106,8 @@ static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn, if (!ti->type->iterate_devices) goto out; - ret = ti->type->iterate_devices(ti, fn, data); + ti->type->iterate_devices(ti, fn, pr); + ret = 0; out: dm_put_live_table(md, srcu_idx); return ret; @@ -3119,10 +3121,24 @@ static int __dm_pr_register(struct dm_target *ti, struct dm_dev *dev, { struct dm_pr *pr = data; const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops; + int ret; + + if (!ops || !ops->pr_register) { + pr->ret = -EOPNOTSUPP; + return -1; + } + + ret = ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags); + if (!ret) + return 0; + + if (!pr->ret) + pr->ret = ret; - if (!ops || !ops->pr_register) - return -EOPNOTSUPP; - return ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags); + if (pr->fail_early) + return -1; + + return 0; } static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key, @@ -3133,19 +3149,29 @@ static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key, .new_key = new_key, .flags = flags, .fail_early = true, + .ret = 0, }; int ret; ret = dm_call_pr(bdev, __dm_pr_register, &pr); - if (ret && new_key) { - /* unregister all paths if we failed to register any path */ - pr.old_key = new_key; - pr.new_key = 0; - pr.flags = 0; - pr.fail_early = false; - dm_call_pr(bdev, __dm_pr_register, &pr); + if (ret) { + /* Didn't even get to register a path */ + return ret; } + if (!pr.ret) + return 0; + ret = pr.ret; + + if (!new_key) + return ret; + + /* unregister all paths if we failed to register any path */ + pr.old_key = new_key; + pr.new_key = 0; + pr.flags = 0; + pr.fail_early = false; + (void) dm_call_pr(bdev, __dm_pr_register, &pr); return ret; } -- 2.7.4